1. Field of the Invention
The present invention relates to a lubricating system for an internal combustion engine wherein an oil relief valve dipped in oil in an oil pan is connected to a halfway part of a feed oil passage connecting an oil pump and an oil filter.
2. Description of the Background Art
Such a lubricating system is disclosed in Japanese published examined utility model application No. Sho 60-40804, Japanese published examined utility model application No. Sho 61-35684 for example and others.
In the above conventional type, an oil relief valve is arranged with the pressure receiving surface of its plunger directed upwardly and a relief port provided in the housing of the oil relief valve to be opened or closed by the plunger is located in an upper position near to an oil level in the oil pan. Therefore, air at the oil level is mixed in relief oil discharged from the relief port of the oil relief valve and is readily frothed, and oil in which air is mixed may be led to the oil pump. In the above Japanese published examined utility model application No. Sho 61-35684, an oil relief valve is covered, however, in such a construction, a cover is required and the number of parts is increased.